Low contact pressure switch



R. A. CRANE LOW CONTACT PRESSURE SWITCH June 26, 1962 Filed Aug. 24, 1959 P055 /-P 7' A. CRHNE ATTORNEY United States Patent C) M 1 3,041,421 LOW CONTACT PRESSURE SWITCH Robert A. Crane, Concord, Calif., assignor to The Dow Chemical Company, Midland, Mich., a corporation of Delaware Filed Aug. 24, 1959, Ser. No. 835,793 4 Claims. (Cl. 200-61.18)

This invention relates to a low contact pressure switch which is particularly useful in connection with electrical signal circuits, such as those utilized for giving indications of broken filaments, threads, and similar very fine materials.

In the past, various means have been devised for supplying electrical signals to control, recording, and indicating circuits for use as indications that very fine elements have been bro-ken or that the tension on such elements has been released. Such electrical signal indicat ing or signal initiating devices have been used in connection with the testing of fine filaments and in various machines utilizing threads or similar fine filaments to indicate when the filaments are broken and for providing a control circuit for stopping the equipment or machine which is utilizing the thread or filament in its operation or which is performing a function connected with the thread or filament, such as a knitting or weaving machine or a machine which may be used for makingor treating the threads or filaments. These machines comprise a great variety of equipment, and may also include equipment used for dyeing various fibers or otherwise treating such fibers or for insulating or otherwise finishing fine filaments, such as fine electrical conductors. Various types of switches and other electrical signal initiating means, such as photoelectric circuits, have been used for these purposes.

In most instances there is an undesirable time lag between the breakage of the thread or filament and the initiation of the electrical signal, so that the equipment is not stopped immediately, or as soon as might be desired, or in the case of test equipment an erroneous measurement results because of the time delay. It is highly desirable, therefore, that the switch or other means which initiates the electrical indicating signal have as short a time of response as possible.

An object of this invention is to provide an improved low contact pressure switch which is particularly adaptable to give a substantially instantaneous electrical signal upon the occurrence of a predetermined condition, such as the breakage of a thread or filament.

Another object of this invention is to provide an improved and simplified low contact pressure switch having a minimum of operating parts.

A further object of this invention is to provide an improved low contact pressure switch particularly adaptable for use in single filament fiexure fatigue testers.

Further objects and advantages of this invention will become apparent from the following description referring to the accompanying drawing, and the features of novelty which characterize this invention will be pointed out with particularity in the claims appended to and forming a part of this specification.

In the drawing:

FIG. 1 is a perspective view of a flexure fatigue tester provided with an embodiment of an improved and simplified low contact pressure switch made in accordance with this invention;

FIG. 2 is an enlarged perspective view of a low contact pressure switch of the type illustrated in FIG. 1;

FIG. 3 is an elevational view, in half section, taken along a plane indicated at 3-3 in FIG. 2;

FIG. 4 is a top plan view of the low contact pressure switch shown in FIGS. 2 and 3, and

3,041,421 Patented June 26, 1962 ICC FIG. 5 is a bottom plan view of the low contact pressure switch shown in FIGS. 2, 3, and 4.

Referring to the drawings, an improved low contact pressure switch is illustrated embodying the present invention which comprises only two main switch members. One of these members is a simple cup formed of insulating material with a concave surface therein adapted to face upwardly for the reception of the second member which is a simple electrically conductive weight. The concave surface of the cup member is split substantially diametrically thereacross, so as to separate the concave surface of the cup into two separate parts, and these parts are coated with an electrically conductive material, thus providing two electrical contact surfaces which are insulated from each other by the split in the cup.

The weight member may be of any desirable shape sufficiently small to fit into the concave portion of the cup member and sufficiently large to extend across the two split portions of the cup member for electrically connecting them together, without becoming wedged in the split which divides the cup into two portions. This provides a very simple switch structure for providing an electrical signal to a circuit by simply electrically connecting the two electrically conductive surfaces of the cup by a weight which is suspended above the cup on the filament or thread relatively close to the cup, so that on breakage or loss of tension, the weight member will fall into the cup and close an electrical circuit across the two parts of the split cup.

For illustrative purposes, FIG. 1 shows an embodiment of the present invention in connection with a fiexure fatigue tester, which is disclosed and claimed in co-pending application Serial No. 835,794, filed August 24, 1959, of Robert A. Crane and Prentice C. Wharif, Jr., and as signed to the same assignee as the present application. This fiexure fatigue tester is particularly useful for testing a plurality of filaments 7 which may be mounted thereon in any suitable manner, as being adhesively secured to one end to suitable mounting tabs 6. These tabs 6 are adapted to be secured in position on a mounting bar 5 by a plurality of mounting pins 5' extending through apertures in the mounting tabs 6. The mounting bar 5 is arranged to be cyclically operated to draw the filaments 7 back and forth over a flexing bar 2, and tabs 6', similar to tabs 6, are secured to the ends of the filaments which hang freely over the bar 2, so that weights may be secured to the free ends of the filaments to maintain them under a slight tension and drawn tautly over the fiexure bar.

In this type of device, the weight which is adapted to draw each filament over the fiexure bar 2 very convenien-tly may comprise an electrically. conductive element which forms the circuit closing member of the low contact pressure switch. As shown in FIG. 1, this low contact pressure switch may comprise a cup member 33, which is mounted in the flexure fatigue tester directly under the weight member 21 secured to the tab '6 on the free end of each filament 7. In this manner, the cups can be placed in close proximity to the weight members 21, so that when a filament 7 breaks its respective weight member 21 will fall directly int-o the concave portion of the cup members 33. This can be utilized to give an almost instantaneous electrical signal which will indicate that the respective filament 7 has been broken.

In a fiexure fatigue tester, such as is shown in FIG. 1, counters 22 can be mounted directly [in the tester instrument for registering the number of cycles of operation of the bar 5, which correspond to the number of fiexures of the test filaments 7. The signal provided by the falling of a weight 21 within a switch cup 3L3 can be utilized to stop its respective counter 22 and thus give a direct span r21 measurement of the number of flexing cycles to which the broken filament has been subjected prior to its breakage. Similar arrangements of the improved low contact pressure switch can be utilized for indicating the breakage of filaments, fibers, and similar fine elements for controlling circuits of equipment utilizing or treating the filaments or fibers. These switches can be formed with any suitable concave electrically conductive split cup surface and can utilize any suitable electrically conductive weight, although it has been found that an inverted female conical surface forms one of the most efficient configurations for the concave portion of the cup.

FIGS. 2 to 5 illustrate the details of a low contact pressure switch, of the type shown in FIG. 1, in which the concave portion of the switch comprises such a female conical surface. This conical surface is formed in the cup member 33 in any suitable manner, as by molding it directly into a cylindrical block of insulating material which forms the cup 33. It also may conveniently be formed simply by cutting a long cylindrical rod into sections of the desired cup length and simply machining out the conical cup portion from each cylindrical element. The two electnical contact elements of the switch are formed by placing an electrically conductive layer of material 37 over the inwardly tapered female conical surface of the cup and extending this conductive surface over the outer base 34 of the conical surface and down over the outer sides of the cup, as shown at 41, preferably tapering the outer surface substantially to a point which terminates in a threaded passage 40'. The cup member 33 is split substantially diametrically of the outer conical base 34 by a slot 35 which extends from the outer base 34 to the inner end or apex 34' of the conical surface, so as to divide the cup member into two substantially equal parts. Furthermore, the electrically conductive material 37 preferably does not extend all the way to the apex 34' but stops short thereof, as indicated at 37', thereby providing for completely insulating each of the electrical contact surfaces 37 by the slot 35- and by the space 36 between the end 37 of the surfaces 37 and the apex 34'. Connections to the two electrical contact surfaces 37' may conveniently be made to an external circuit by forming a pair of longitudinally extending passages 38 in the cup member 33. These passages may readily be formed by drilling or molding them directly into the base of the cup member 33, to a depth substantially equal to the distance of the apex 34 from the base of the cup member 33. Electrical conductors 39 and 39" from an external electrical circuit may then be inserted into the passages 38, and set screws 40 can be fastened into the threaded passages 40' so as to engage the ends of the conductors 39 and 39 to fasten them securely in position in the switch cup member 33.

A good electrical connection can conveniently be made between the electrical conductors 39 and 39* and the electrically conductive contact surfaces 37 by simply extending the electrically conductive material which forms the surfaces 37 and 41 into good electrical contact with the heads of the set screws 40. This is very efficiently and conveniently done by forming the electrically conductive surfaces by means of any suitable electrically conductive paint, such as a silver pigment paint, which may be applied in any suitable manner, to form the conical surfaces 37, the outer conductive base surface 34, and the triangular conductive surfaces 4 1. It then is simply necessary to extend the triangular painted surface 41 to the aperture of the passage 40' and to paint over the head of the set screw 40, in order to form a complete electrical circuit between the conductors 39 and 39" and the inner split female conical surfaces 37.

As shown in FIG. 1, the two electrical contact surfaces 37 are open circuited as long as weights 21 are held suspended above the cups 33 out of contact with the electrically conductive surfaces 37. Breakage of any of the filaments 7 to which the weights 21 are secured 4 results in such weights falling into their respective cup members 33. These weights 21 may be of any suitable form and preferably are relatively light, so as to minimize the tension upon the filaments to which they are attached, as it is only desirable that the weight should be suificient to hold these filaments taut with a minimum of tensile stress thereon due to the weights 21. The illustrated weights include a main weight portion 21 and a cross-arm 21 which is slightly less than the diameter of the outer base of the conical surface to which the contact surfaces 37 are attached, so that the weight member 21 can fall into the cup member :33 and, in so doing, will be retained therein while extending across the slot 35 and thus electrically connecting the twoelectrically conductive surfaces 37 on the two parts of the split cup portion of the member 33. The cross-arm 21. preferably is formed with angularly extending ends 21" of a length greater than the width of the slot 35, so that, when the weight 21 falls into the cup member 33, the angularly extending ends 21 will prevent the cross arm 211' from becoming lodged in the slot 35, thereby assuring the formation of an electrical connection between the two split electrically conductive surfaces 37 through the crossarm 21'.

In order further to assure the proper formation of an electrical circuit between theconical contact surfaces 37 through the weight cross-arm 21', the weight member 21 preferably is formed with a longitudinally extending guide rod portion 47 and the cup member 33 is formed with a longitudinally extending passage 46, which extends from the lower end of the member 33 to the apex or small end 34 of the conical surface on which the contact surfaces 37 are formed. With this construction when a weight 21 falls within a cup member 33 the guide rod portion 47 thereof will fall into the passage 46 and will guide the weight '21 downwardly into the cup member until the cross-arm portion 21 thereof contacts the two electrically conductive surfaces 37. This also assists in preventing accidental dislodgrnent of a weight 211 from its electrical contact with the surfaces 37 after it has fallen into a cup member 33, as it tends to minimize possible rebound of a weight out of its respective cup.

In this manner, when a filament, to which a weight 21 is attached, breaks or loses its tension, its respective weight 21 will fall into a split cup member 33. The weight cross-arm portion 21 thereof is guided into electrical contact with the concave split female conical surface layers 37, thereby electrically connecting these surfaces and completing an electrical circuit through the conductors 39 and 39, so as to supply a signal to the circuit in which these conductors 39 and 39 are connected.

This provides a very simple two-member switch, which' will close an electrical circuit in response to the very low contact pressure provided simply by the small pressure of the light weight 21.

While a particular embodiment of this invention has been illustrated and described in connection with a special application thereof, modifications of the mechanical and electrical components may readily occur to those skilled in the art. It is to be understood, therefore, that this invention is not to be limited to the particular details disclosed, and it is intended in the appended claims to cover all modifications within the spirit and scope of this invention.

I claim:

1. A switch comprising a cup member of electrically insulating materials having a concave surface therein with the enlarged outer base thereof adapted to face upwardly for reception of an electrically conductive circuit closing element, said cup member having a slot therethrough extending diametrically across said concave surface splitting the same into two parts, said cup member having a guide passage extending longitudinally thereof from the inner end of said concave surface, an electrically conductive surface material on both parts of said split concave surface extending from short of the inner end thereof to the outer base and over said outer base and outer side of said cup to external points separated by said slot thereby maintaining the conductive surfaces on said parts insulated from each other, and an electrically conductive circuit closing element adapted to be arranged over said cup member out of contact therewith and to be lowered into said cup in response to predetermined conditions to connect electrically said electrically conductive surfaces, said circuit closing element having a guide portion adapted to extend toward said cup when out of contact therewith and to fit into said guide passage when lowered into said cup to aid in assuring good electrical contact of said circuit closing element with said conductive material on said cup.

2. A switch comprising a cup member of electrically insulating material having an inwardly tapered surface for reception of an electrically conductive circuit closing element, said cup member having a slot therethrough splitting the same into a plurality of parts, an electrically conductive surface on said inwardly tapered surface extending to external points separated by said slot thereby maintaining the conductive surfaces on said parts insulated from each other, an electrically conductive circuit closing element adapted to be suspended over said cup member out of contact therewith and having cross-arms of a length less than the outer diameter of said tapered cup surface and adapted to be lowered into said cup into contact with said conductive surfaces in response to predetermined conditions to connect electrically said electrically conductive surfaces, and means for electrically connecting said conductive surfaces on said split parts in an electrical circuit.

3. A switch comprising a cup member of electrically insulating material having an inwardly tapered surface for reception of an electrically conductive circuit closing element, said cup member having a slot therethrough extending diametrically thereacross splitting the same into two side parts, an electrically conductive surface on both parts extending to external points separated by said slot thereby maintaining the conductive surfaces on said parts insulated from each other, an electrically conductive circuit closing element adapted to be suspended over said cup member out of contact therewith and having crossarms of a length less than the outer diameter of said tapered cup surface with an angular extension on the end of each cross-arm of a length greater than said slot and adapted to be lowered into said cup into contact with said conductive surfaces on both of said cup parts in response to predetermined conditions to connect electrically said electrically conductive surfaces on said two parts of said cup, and means for electrically connecting said conductive surfaces on said split parts in an elec-' trical circuit.

4. A switch comprising a cup member of electrically insulating material having a female conical surface therein with the base thereof adapted to face upwardly for reception of an electrically conductive circuit closing element, said cup member having a slot therethrough extending diametrically across said female conical surface splitting the same into two parts, an electrically conductive surface comprising a thin coating of conductive paint on both parts of said split female conical surface extending from short of the apex thereof and over said outer base and outer side of said cup to external points separated by said slot, an electrically conductive circuit closing element adapted to be suspended over said cup member out of contact therewith and to be lowered into said cup into contact with said conductive surfaces on both of said cup parts in response to predetermined conditions to connect electrically said two parts of said split female conical electrically conductive surface, and means for electrically connecting said conductive surfaces on said split parts in an electrical circuit.

References Cited in the file of this patent UNITED STATES PATENTS 2,182,300 McCandless Dec. 5, 1939 2,897,307 Johnston July 28, 1959 2,963,562 Mishler Dec. 6, 1960 

